FS561 – Physiology of Woody Plants  Fall 2009

OBJECTIVES AND REFERENCES FOR OCTOBER 1

There is no required reading assignment for today

 

Useful supplementary information:

 

radiation references -- Includes tables from appendices in Hall et al., 1993, Photosynthesis and Production in a Changing Environment, and J.W. Hart, 1988, Light and Plant Growth

 

Jones, H.G. et al.  2003.  Radiation measurements for plant ecophysiology.  J. Exp. Bot. 54:879-889

 

Humidity -- A nice on-line reference that includes a link to "humidity and how it is expressed"

Learning Objectives:

After attending the lecture and additional reading as necessary, you should be able to:

  1. Use and interpret the following terms and acronyms in a way that demonstrates your understanding of the meanings:  fluence; fluence rate; flux density; radiometric units; quantum units; photometric units; PAR, PPFD, APAR, radiation; shortwave and longwave radiation; visible, ultraviolet and near-infrared radiation; radiance and irradiance; direct and diffuse irradiance; absolute humidity; vapor pressure; saturation vapor pressure; dew point temperature; relative humidity; vapor pressure deficit
  2. Calculate the amount of energy in radiation given the quantum flux, or conversely calculate the quantum flux given the energy; explain why and how the efficiency of energy use in photosynthesis varies through the photosynthetically active spectral range
  3. Explain why the quantity of solar radiance is often described as a rate (e.g. Watts), whereas irradiance is more typically described as a flux density (e.g. Watts m-2) or fluence (e.g. J m-2)  [this was not covered explicitly in lecture or references – think and talk about it].
  4. Given the amount of total (i.e., “full spectrum”) solar irradiance on a surface in radiometric units, estimate the amount of photosynthetically active irradiance in both photometric and quantum units.
  5. Give appropriate units for quantifying light for particular applications and suggest appropriate applications for various units
  6. Use Lambert’s cosine law to calculate the change in irradiance on a surface as the angle of incidence of light changes; explain what it means for a light sensor to be “cosine-corrected”
  7. Interconvert different units of humidity given necessary information, such as temperature or air pressure
  8. Explain qualitatively how (and why) a) temperature affects relative humidity for a given vapor pressure; b) dew point temperature is a measure of humidity, even though we use units of temperature to measure it. 
  9. Sketch graphs to illustrate the general trends of change in various measures of humidity as temperature or air pressure change